Cosmology with active galactic nuclei

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My research in Observational Cosmology concentrates on Active Galactic Nuclei (AGNs), commonly known as quasars, bright stellar objects of enormous luminosity, the powerhouse centres of large galaxies. It is vital to understand these objects as they must be involved in galaxy formation and evolution - their properties are tightly correlated with those of the host galaxies. Whatever their mysterious physics, they are luminous beacons able to trace mass throughout the observable universe. My proposal concerns two aspects of my AGN research:(1) The 'unified model' of radio AGN has it that radio quasars and radio galaxies are the same  - the different appearance is simply a matter of projection effects involving a central torus and relativistic beaming. We see a quasar if our line-of-sight coincides with the projection axis, a double-lobed radio galaxy otherwise. Research 1997 to 1999 showed us how we could use bulk statistics of quasars and radio galaxies to obtain the  physics of AGN beaming systems. We now have a flood of new data to allow us to do the analysis properly. Thus through analysis of bulk statistics, we can establish the central physics of the most luminous objects in the Universe - we can find how quasars work.(2) My second project concerns Dark Energy. Our current 'concordance cosmology' has 5% of the matter in the Universe as luminous, 25% as dark and unobservable directly, and 75% inferred as Dark Energy of unknown nature. Direct assurance of Dark Energy existence can come through the 'Integrated Sachs-Wolfe' (ISW) effect: a correlation between number fluctuations in the surface density of sources in a radio survey and fluctuations in the cosmic microwave background could only result if the Universe were currently dominated by Dark Energy. Early tests by others have been positive, in agreement with inference. I wish to use a programme of mass identifications of the sources in a large radio survey to work out the contribution to the correlation in each redshift shell of the survey. This will define Dark Energy  properties as a function of cosmic epoch, constraining its nature. Here is a new tool with which to explore the most challenging issue in cosmology.